Circuit breaker



Sept. 26, 1933. c. w. KUHN CIRCUIT BREAKER Original Filed July 12, 1928 in n III/II l ATTORNEY Patented Sept. 26, 1933 UNITED STATES CIRCUIT BREAKER Renewed July 28, 1932 Application July 12, 1928. Serial No. 292,228

8 Claims.

This invention relates to circuit breakers and more particularly to the type which responds selectively to a low current or a high current.

The invention has among its objects to provide a simple and efiicient circuit breaker having a retarded response to overloads up to a predetermined value and a substantially instantaneous response to overload in excess of such value.-

Another object of the invention is a circuit breaker having a single electromagnet for op erating under either condition of response.

Another object of the invention is a circuit breaker in which the retarded response is under the control of a thermal element of the melting solder type.

Other objects of the invention will hereinafter appear.

In the accompanying drawing,

Fig. 1 illustrates one embodiment of my invention,

' Figure 2 shows a more detailed view of the thermal responsive element illustrated in Figure 1,

and I Figure 3 shows another form of another embodiment of the invention.

Referring to Figure 1 of the drawing, the circuit breaker comprises an electromagnet 1 having a core 2 and an armature 3 which is provided with a contact 4, the latter engaging the stationary contact5. The armature 3 is connected with a lever '7 pivoted at 8, by means of a stud 9 and a compression spring 10 in such a manner that as long as the lever 7 is free to move, the ar-' mature 3 and the lever '7 oscillate as one element around the pivot 8. The magnet l-is energized by a coil 11. The outer end of lever 7 carries a pin 12 the lower end of which is guided in a bearing 13.' Rivete'd to the pin is a spring 14 which engages a toothed disk 15 which forms I part of the thermal element.

The thermal element consists of a stationary member 16 fastened to a support 1'7. The member 16 has a recess 16:: in which projects a pin 18 riveted to the disk 15. The pin 18 is normally 4 soldered by means of a small quantity of low melting point solder 19 to the support 16. A heating coil 20 serves to heat the solder 19, and if the current exceeds a certain amount for a predetermined time, the solder 19 melts, thereby freeing the pin 18 from the support 16 and permitting it to spin.

I have illustrated the circuit breaker in combination with a motor 21which receives current from the lines L and I. under the control of a magnet switch 22 having a main contact 23 and an auxiliary contact 24 and energized by a magnet coil 25. The momentary contact push button 26 serves to start and stop the equipment.

The equipment operates as follows:

When the push button 26 is momentarily deno pressed the current flows from line L over contacts 5 and 1 of the circuit breaker through coil 25 of the magnet switch 22 through the push button 26 to line L the magnet coil 25 thereby be-= comes energized and closes contacts 23 and 24. 35 Closure of the contact 24 bypasses the push button, so that the switch will stay closed upon release of the former. The current to the motor flows from line L through coil 11 of magnet 1 through the heater coil 20 over contact 22 and through the motor winding to line L If the current to the motor should be excessive for a. certain length of time, the heater coil heats up through conduction and radiation the support 16 and the pin 13 until ultimately the solder 19 melts 7a and thereby frees the disc 15.

When the coil 11 is energized a pull is exerted on the armature 3, which tends to rotate the armature and the lever '2 clockwise, but this rotation is prevented by the engagement of the spring 14 with the disc 15. As soon as the solder melts and the disc is free to move, the armature 3 is free to move downward under the effect of the magnet and it thereby opens the circuitbetween contacts 4 and 5, thus deenergizing the magnet 25 and opening the circuit to the motor.

If an excessive overload should occur, the magnet 11 attracts armature 3 with a sufficient force to overcome the tension of the spring 10, thereby opening the circuit between contacts 4 and 5 substantially instantaneously. After the circuit has opened no current flows through the coils 11 and 20, and a light spring 27 returns the armature to the closed circuit position and thereby also returns the pin 12 to its normal position, thus, again causing engagement between the latch 14 and disc 15. As soon as the solder has hardened the circuit breaker is again in the operative condition, and it will respond again to current conditions of the circuit as heretofore described.

The current at which the thermal element responds may be varied in various ways, for instance, as shown in my co-pending application No. 93,044, dated March 8, 1926, which became Patent No. 1,732,477 on October 22, 1929, and the calibration of the magnet to cause it to respond to various currents may also be varied by means of various well known expedience. It is also possible to vary the current at which the magnet will respond instantaneously by changing the tension of the spring 10 by means of the screw 9.

Referring to Figure 3 the circuit breaker comprises an electromagnet having a frame 30, an armature 31 and a magnet coil 32. The armature or plunger 31 is provided with a recess 33, the lower end of which is threaded to receive the adjusting screw 34. Inserted in the upper smaller diameter end of the recess is a pin 35 which has at its lower end an abutment 36. A spring 37 is mounted in the'recess one end thereof bearing against the adjusting screw 34 and the other against abutment 36 of pin 35. Pin 35 is mounted in such a mannerthat it can yield sideways being normally biased to the vertical position by the spring 38. The plunger 31 is also provided with a second pin or extension 39. The frame 30 carries at its upper end a stop 40 for engagement with the plunger 31 when the latter is in its attracted position. Surrounding the stop 40 is a circular casting 41 of high electrical conductivity which forms a short circuited secondary winding with respect to the magnet coil 32. The casting 41 is provided with a projection 42 which sup-' ports a pin 43, the pin being normally connected to said extension by means of a low temperature solder. The pin carries the toothed disc 44 in the manner illustrated in Fig. 2. On top of the electromagnet is mounted the stationary contact 45 which normally engages the movable contact 46, the latter being biased by means of its spring arm 47 to normally circuit closing position. A magnetic shunt in the form of a plug 48 is inserted in the side of the electromagnet frame 30 in such a-manner that its distance from the plunger 31 can be regulated by means of its threaded connection with the frame. A stop 49 on the lower-part of the-magnet frame serves to limit the downward travel of the plunger 31. In operation'the coil 32 is connected in series with the load circuit to be protected, and thus the current in the coil and the flux set up thereby vary in accordance with the load.

The operation of the device is as follows:

Under the influence of the current in load circuit the magnet is energized and the stop 40 tends to attract plunger 31 under the influence of the magnetic field. A part of the flux is shunted around the plug 48 and the smaller the distance between plug 48 and the plunger 31 the smaller'is the attraction of the plunger by the stop 40 for a given current. The upward movement of the plunger is prevented by the pin 35 which engages the toothed circumference of the disk 44. But, if the current is of a sufficiently high value it ultimately compresses the spring 3'7 and permits the plunger to move upward. In doing so it carries with it the pin 39 and the latter opens the circuit between contacts 45 and 46, the circuit arrangement for the control circuit being the same as illustrated in Fig. 1.

The flux which is produced by the current in coil 32 induces currents in the short circuited secondary 41 thereby heating the same. If the current in coil 32 is above a certain value the current induced in the short circuited secondary is sufiicient to raise its temperature and with it the temperature of bracket 42 to a point that the soldered joint between pin 43 and the bracket is melted, thus permitting the disc 44 to rotate and freeing the plunger 31 from the restraint put upon it by engagement of the pin 35 with the.

disc 44. The plunger is therefore free .to move so that pin 39 opens the circuit between the contacts 45 and 46. As soon as the current in the load circuits has been interrupted the magnet 30 is deenergized and the plunger drops back to its normal position. To permit pin 35 to pass the disc 44 in its downward travel the spring 38 permits a slight sidewise motion of said pin while at the same time it holds it in engagement with the disc 44.

By adjusting the shunt 48 the ratio between the current in the coil 32 and the current induced in the short circuit winding 41 is also adjusted so that the adjustment of this shunt 48 not only adjusts the current at which the circuit breaker opens instantaneously but also the lower current at which the circuit breaker opens the circuit under a delayed action.

It is of course obvious that instead of short circuiting coil 41 it would be possible to provide a heating coil around the'pin 43 similar to that shown in F. g. 2, which is connected in series with the coil 32 and it is equally obvious that the soldered latch could be provided with an adjustment similar to that shown in my co-pending application No. 93,044, dated March 8, 1926, which became Patent No. 1,732,477 on October 22, 1929, to provide an adjustment by means of the shunt 21.

Various other modifications of the device will be obvious to those skilled in the art.

The use of the device in a circuit is similar to the use of the device as shown in Figure l and therefore need not be described again.

Also it is of course obvious that the adjusting screw 34 provides means whereby the resistance offered by the spring 37 to upward movement of plunger 31 may be increased or decreased at will.

What I claim as new and desire to secure by Letters Patent is:

1. In combination, an electromagnet, a thermal element, a switch operable by said electromagnet subject to an influence by said thermal element, said switch being operable substantially instantaneously by said electromagnet when excited by a current exceeding a certain value and being subjected by said thermal element to delayed operation by said electromagnet when the exciting current is of lesser value, means for adjusting the current at which said electromagnet responds instantaneously and separate means for adjusting the influence of said thermal element.

2. In combination, an electromagnet subjected to a varying current, a thermal element having a heating coil subjected to a correspondingly varying current, a switch operable by said electromagnet subject to an influence by said thermal element, said switch being operable substantially instantaneously by said electromagnet when excited by a current exceeding a given value and being subjected by said thermal element to a delay in its operation by said electromagnet when the exciting current is of lesser value, means for adjusting the current at which said electromagnet responds instantaneously and separate means for adjusting the influence of said thermal element.

3. In combination, a switch, an electromagnet for operating said switch, means affording a given resistance to operation of said switch by said electromagnet, said means including a thermal device responsive to reduce\the aforementioned resist-' ance of said means, and further including an adjustment whereby suclrresistance may be varied at will, and means whereby with a given adjustment of the aforementionedmeans the sensitiveness of response of said switch to said electromagnet may be varied. 150

4. In combination, a switch, an electromagnet for operating said switch, means affording a given resistance to operation of said switch by said electromagnet, said means including a thermal device responsive to reduce the aforementioned resistance of said means, and further including an adjustment whereby such resistance may be varied at will, and a magnetic shunt for said electromagnet whereby with a given adjustment of the aforementioned -means the sensitiveness of response of said switch to said electromagnet may be varied.

5. In combination, an electromagnet, a switch operable by said electromagnet, a thermal element, said electromagnet and said thermal element being affected by currents having a given ratio, an adjustable connection between said electromagnet and said thermal element for permitting said switch to operate instantaneously when said currents exceed a given value, said thermal element also permitting operation of said switch at a lower value of said current, but subject to a time delay.

6. A relay including an electromagnet, having an armature and a coil excited by alternating current, a switch operable by said armature, a thermal element subjected to a current induced therein by said alternating current, and adjustable means between said thermal element and said armature to restrain the latter for a given time from operating said switch in response to abnormal currents below a given value, and means foradjusting the relation between said alternating current and said induced current.

7. In combination, an alternating current electromagnet, a thermal element inductively coupled to said electromagnet, a switch operable by said electromagnet and subjected to an influence by said thermal element, said switch being operable substantially instantaneously by said elec tromagnet when excited by a current exceeding a certain value and being subjected by said thermal element to delayed operation by said elec tromagnet when the exciting current is of lesser value, means for adjusting the current at which said electromagnet responds instantaneously, and separate means for adjusting the influence of said thermal element.

8. In combination, an electromagnet, a switch operable by said electromagnet, and a thermal element, said electromagnet and said thermal element being afiected by currents having a given ratio, an adjustable connection between said switch and said electromagnet to provide for operation of the former instantaneously when said currents exceed a given value, and additional means for adjusting the current value at which said electromagnet responds; said thermal element permitting operation of said switch at a, lower value of said currents, but subject to a time delay.

CLARENCE 'WILBUR KUHN. 

